1 Other common diisocynates include hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI) and isophorone diisocyanate (IPDI) (Fig. At a CO concentration of 10 ppm, impairment of judgement and visual perception occur; exposure to 100 ppm causes dizziness, headache, and weariness; loss of consciousness occurs at 250 ppm; and 1000 ppm results in rapid death. The authors declare that they have no competing interests. The authors proposed that once formed, these compounds could partially polymerise with volatilised TDI in the vapour phase to produce Woolleys yellow smoke. Thermosets are cross-linked polymer molecules which, on heating, do not melt but will eventually decompose. Substituted aromatics containing electron withdrawing groups further increase the reactivity of isocyanates by increasing the partial positive charge on the isocyanate carbon via a resonance withdrawing effect. When polyurethane and polystyrene burn, they create a very smoky fire that . However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. However, as fires tend to grow exponentially, they do not produce constant concentrations of asphyxiant gases. VOCs and Other Toxic Chemicals in Mattresses: What to Know The fire department was not immediately called, so the oil burned completely. At sufficiently high concentrations, or when attached to submicron particles, such as soot, most irritants can penetrate deeper into the lungs, causing pulmonary irritation effects which may cause post-exposure respiratory distress and death, generally occurring from a few hours to several days after exposure, due to pulmonary oedema (flooding of the lungs) (ISO 13571 2007). It is likely that the fire toxicity of fire retarded polyurethane materials is largely dependent on the specific fire retardant present. Higher temperatures resulted in the volatilisation of most of the polyurethane precursors via the formation of lower molecular weight compounds. The carbon dioxide release by the reaction in Scheme2 can act as a blowing agent in polyurethane foam production and up to a point the amount of water added will be inversely proportional to the density of the foam. The three-compartment test consisted of a 2.43.72.4m burn room, a 2.44.62.4m corridor and a 2.43.72.4m target room where samples would be taken. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). The authors noted that in both the flaming and non-flaming combustion of the polyurethane foam, the concentrations of toxicants did not reach high enough concentrations to predict deaths. For the range of materials investigated, the authors also noted that those containing fire retardants (including the CMHR-PUF and PIR) resulted in a higher recovery fraction of fuel N as HCN. Thermal decomposition of polyurethanes is usually the reverse of polymerisation, resulting in the formation their precursor functional compoundsdiisocyanates, diamines and dihydroxy compounds. While several authors work has focused primarily on the nitrogenous products of decomposition, other publications have focused on the production of other compounds such as carbon monoxide. Toxic product yields frommaterials involved in fires depend on a number of factors. From this, the library of data was sorted into categories of combustion/pyrolysis conditions, material/product, type of test animal and toxicological endpoint. Historically, material-LC50 data has been reported directly based on animal lethality testing, however due to the declining use of animal testing in fire toxicity assessment, calculations based on standard lethality data(such as ISO 13344 1996) are more commonly used. However, as noted by Paabo and Levin (1987), many studies into the decomposition of polyurethane foams do not differentiate between flaming and non-flaming decomposition, and focus on the temperature of decomposition rather than the presence of flames. Once the material ignited, the yield of HCN increased to 3.8mgg1. Further reactions occur with amines, water, ureas, urethanes and even other isocyanates to produce a diverse range of functional groups including urethanes, ureas, isocyanurates, carbodiimides and uretdiones. (2007) suggests that their yields are not heavily dependent on the ventilation conditions and that the yields would likely only increase by a small amount during under-ventilated flaming. However, while the char produced when the polymer was heated at 370C contained only 20% of the total nitrogen from the polymer, 40% of that (8% of the total nitrogen in the polymer) was recovered as HCN when the char was burned at 600C. At high concentrations nitric oxide is rapidly oxidised in air to form nitrogen dioxide, however, at the concentrations found in fire gases, most of the nitric oxide remains unoxidised. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Fire Research Notes 951:p117. Appropriate formulation affords a degree of control over the cross-linking in the polymer without the need for additional cross-linking agents. 1995). Top of Page. The most commonly reported adverse health effects after airborne isocyanate exposure is asthma due to sensitisation (Piiril et al. 12, feeds the sample (typically around 25g of pellets or granules) into its hot zone at a fixed rate, under a controlled air supply, inside a horizontal silica tube of diameter 48mm, allowing adequate mixing of fuel and oxidant. (3) Polyurethane foam mattresses, dubbed "solid gasoline", can give off toxic fumes that may be linked to short- and long- term health conditions. In most countries, there are no regulations covering the fire toxicity of building components, or for most road vehicles, including goods vehicles in tunnels. Spray Foam Insulation: Helping Achieve Sustainability. (2011) Aerospace series - Burning behaviour of non-metallic materials under the influence of radiating heat and flames - Determination of gas components in the smoke; ABD 0031 Fire-Smoke-Toxicity (FST) Test Specification (Airbus Industries); Boeing BSS 7239, Test method for toxic gas generation by materials on combustion. This prompted the authors to perform further studies in order to understand why allowing the foam to smoulder increased the yield of HCN during flaming combustion. The cone calorimeter (ISO 56601 2002) is probably the most widely used apparatus for measurement of flammability properties such as ignitability and heat release rate (Schartel & Hull 2007). Urethane Foam Health Effects | livestrong The authors acknowledged that the lower nitrogen recovery fraction for the flexible foam could be due to fuel nitrogen being lost as isocyanates, which are known to escape into the effluent plume, while for rigid foams they are more likely to be trapped in the burning solid (Woolley & Fardell 1977). It forces combustion by driving the sample into a furnace of increasing heat flux at a fixed rate, so that, by running several tests with the same material with different ventilation conditions, each fire stage can be replicated by steady state burning. Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. April 30, 2021 April 16, 2021 by Shobita Ravichandran. Polymer Degradation and Stability 93:p20582065, Tewarson A (2002) SFPE Handbook of Fire Protection Engineering, 3rd ed. 50 Polyurethane and polyisocyanate both release polyols and isocyanates during blowing, but the rates diminish rapidly over time as the product cures, provided they dialed in the temps & chemical mix correctly. Hazwoper lesson 3 Toxicology Flashcards | Quizlet The test conditions were designed so that the fire conditions met the ISO 19706 (2007) fire type 2 (well-ventilated flaming fire <0.75) and fire type 3b (post-flashover fire in large or open compartments ~2.0). (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. This step dramatically reduced fire deaths, which was considered a triumph at the time. Foams Under Laboratory Conditions, Fire Research Note, No 1039. The revised protocol is based on continuous sampling of the fire effluent. This amine may then undergo further reaction with other isocyanates present to produce a urea (Scheme3). 9). International Association for Fire Safety Science, Ravey M, Pearce EM (1997) Flexible Polyurethane foam. However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. The non-flaming decomposition of non-fire retarded polyurethane foams in air is generally quite well understood and comparable to the inert atmosphere decomposition, in terms of both products and mechanisms. Elemental analysis of the polymers showed that the CMHR-FPUR contained 8.22% nitrogen by weight and the PIR contained 6.15% nitrogen by weight. This char can decompose further, leaving behind a residue at >800C, to produce simple organic fragments and some polycyclic aromatic hydrocarbons (PAHs). The authors did not specify which analytical methods were used in the quantification of the fire gases, only that they were sampled via a sampling bag. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100250mgg1. The smoke density chamber (ISO 5659-2) showing a sampling probe for fire smoke toxicity. Bott et al. The widespread use of flexible polyurethane foams in furniture and other upholstery, where they are usually covered in some kind of fabric has prompted some authors to investigate the effects of covering the foam on the yield of toxic products. Most bench-scale methods have non-constant combustion conditions, such as those in closed chambers exposed to a constant source of heat, including the smoke density chamber (SDC) (ISO 56592 2012), and static tube furnace tests, such as the NF X 70100 (2006). Fire Technology 51:p213217, Blais M, Carpenter K (2015) Flexible Polyurethane Foams: A comparative measurement of toxic vapors and other toxic emissions in controlled combustion environments of foams with and without fire retardants. The average well-ventilated yield of HCN was found to be 4mgg1, while it was 9mgg1 for under-ventilated conditions. Fire Hazards of Insulation Materials | American Family Insurance Additionally, the authors reported a yield of 1315mgg1 of CO, 1.41.5mgg1 of HCN, and 1012mgg1 of NO. In 1975, California passed flammability standards known as Technical Bulletin 117 (TB117), which required polyurethane foam and fabrics produced in state to be treated with flame-retardant chemicals . (1985) when a flexible polyurethane foam was first heated at a temperature below its auto-ignition temperature, followed by flaming combustion of the remaining char and residue at a higher temperature. The toxic effect of carbon monoxide is characterised by a lowered oxygen-delivery capacity of the blood, even when the partial pressure of oxygen and the rate of blood flow are normal. Known as "solid gasoline" in the insurance industry, once a polyurethane fire starts, it usually results in a total loss of property and loss of life, according to Federated Insurance. In the large scale test room, the sample smouldered for 1.5 to 2h, resulting in a HCN yield of 1.03mgg1. Chem Co., Dow, Hertzberg T, Blomqvist P, Dalene M, Skarping G (2003) Particles and Isocyanates from Fires. 1986). In the gas phase, isocyanates, amines and yellow smoke will begin to decompose at >600C into low molecular weight nitrogen containing fragments (such as benzonitrile, aniline and hydrogen cyanide (HCN)). ISO 19706 (2011) Guidelines for assessing the fire threat to people. Again, above 600C the compound and any yellow smoke present was decomposed into smaller volatile fragments. The authors made this assertion based on the yield of average CO from post-flashover fires being 2009mgg1. (1981) reported similar data by analysing the inert-atmosphere pyrolysis of a series of biscarbamates to act as model compounds representing polyurethane foams. The applied heat flux must be large enough for burning to continue at oxygen concentrations as low as 5%. Fire Safety Journal 40:439465, Aneja A (2002) Chapter 2, Structureproperty Relationships of Flexible Polyurethane Foams, PhD. Hydrogen cyanide is approximately 25 times more toxic than carbon monoxide through the formation of the cyanide ion, which is formed by hydrolysis in the blood (Hartzell 1993). Further to this, a similar pattern began to emerge in the injuries of fire victims (Fig. 95% of the demand for polyurethanes is situated in North America, Asian-pacific, and European markets; with demand expected to increase in Eastern Europe and South America in the next 1015 years. (1969) reported the decomposition of rigid polyurethane foams in both nitrogen and air to assess the production of CO, HCN and NH3. Reliable rate of heat release, fire effluent toxicity and smoke generation data are all essential components of such an assessment. Technology, Gaithersburg MD, Babrauskas V, Levin BC, Gann R, Paabo M, Harris RH, Peacock RD, Yusa S (1991b) Toxic potency measurement for fire hazard analysis, special publication 827, National Institute of Standards and Technology. Substituted ureas decompose between 235 and 250C and carbodiimides decompose between 250 and 280C. Comparison with Room Fire Results, NIST Technical Note 1763, National Institute of Standards and Technology, Gaithersburg, MD, Michal J (1982) Determination of Hydrogen Cyanide in Thermal Degradation Products of Polymeric Materials. In: Fahima Z, Eram S (eds), InTech. Both of the materials showed a clear relationship with the HCN yield increasing with . This value decreased to 18mgg1 at ~2.0. Polyurethanes are named from the presence of theurethane (also known as carbamate) functional group (Fig. The second results in a brief stimulation, followed by severe depression, of respiratory frequency, also starving the body of oxygen, and causing convulsions, respiratory arrest and death (Alarie 2002). Fire Technology 40:p117199, NFPA 269 (2012) Standard test method for developing toxic potency data for use in fire hazard modelling, NFX 70 1001:2006 Fire Tests - Analysis Of Gaseous Effluents - Part 1: Methods For Analysing Gases Stemming From Thermal Degradation, NIOSH (1989) A summaryof health hazard evaluations: Isocyanates, 1989 to 2002, Paabo M, Levin BC (1987) A review of the literature on the gaseous products and toxicity generated from the pyrolysis and combustion of rigid polyurethane foams. The Steady state tube furnace apparatus, ISO/TS 19700. Terence Richard Hull. However, it does suggest that yield of toxic products is effected by covering the foam with another material during flaming combustion. 4 Equation The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. Fire and Materials 25:p7181, Blomqvist P, Hertzberg T, Tuovinen H, Arrhenius K, Rosell L (2007) Detailed determination of smoke gas contents using a small-scale controlled equivalence ratio tube furnace method. (2007). Fire Safety Science 11:p404418, Stec AA, Hull TR, Lebek K (2008) Characterisation of the steady state tube furnace (ISO TS 19700) for fire toxicity assessment. NBSIR 822532. Almost all unwanted fires are diffusion flames, with inefficient mixing of fuel and oxygen(as opposed to the "premixed" flames found in burner/combustion systems). The first step is the decomposition of the urethane bonds to release and volatilise isocyanates up to 300C, with long chain alcohols being left behind in the condensed phase, followed by the alcohols degrading at around 400C. At lower temperatures, decomposition differs, depending on the composition and physical properties of the polymer, although clear trends can be identified. Analysis of the compound, trimethylol propane phosphate (TMPP), by Kimmerle (1976) found it to have a high acute toxicity when tested on rats. However, no amines were detected in the vapour phase. The Purser model, presented in equation1, uses \( {\mathrm{V}}_{{\mathrm{CO}}_2} \) a multiplication factor for CO2 driven by hyperventilation, therefore increasing the FED contribution from all the toxic species, and incorporates an acidosis factor A to account for toxicity of CO2 in its own right (ISO 13344 1996). p 111711128. Their development continued commercially in Germany, eventually leading to a global multibillion dollar industry (Vilar 2002). Purser model, [AGI] is the concentration of inorganicacid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2]0.05. (1990) also reported increased HCN yields when the sample was allowed to smoulder before flaming in similar apparatus as above. Polyurethane foam may be formed at a construction site or installed in the form of board stock (see the "Composite Insulations, Structural Insulated Panels" section). Fire Safety Journal 42:p340365, ISO 12136 (2011) Reaction to fire tests Measurement of material properties using a fire propagation apparatus, ISO 13344 (1996) Estimation of lethal toxic potency of fire effluents, ISO 13571 (2012) Life-threatening components of fire-Guidelines for the estimation of time available for escape using fire data. The yields of acid gases and nitrogen-containing products depend upon the proportion of the appropriate elements in the materials burned and the efficiency of conversion. HCN also causes rapid incapacitation, preventing escape, and then, with CO, contributes to death from asphyxiation. Fire Res 1:p1121. The cribs used in the ISO 9705 tests were constructed from PIR sticks which burned rapidly, albeit with minimal damage to the room. It is inexpensive and easy to install, however, it is a severe fire risk and requires a thermal barrier to make it safe. TNO Report. (2011) developed a mechanism based on both condensed and gas-phase decomposition in air. However, when the TDI was unable to enter the pyrolysis zone, the slower, irreversible decomposition to diaminotoluene (DAT) would occur. 2013). In a report from the same laboratory, Braun et al. The higher flammability of these new furniture products took people by surprise, and has been blamed for an increased number of serious fires and a tripling of fire deaths over 20years (Fig. A review by Paabo and Levin (1987) found that there is no difference in the decomposition products of rigid and flexible polyurethane foams at high temperatures regardless of their differing degradation mechanisms at lower temperatures. At 1000C the hydrogen cyanide produced accounted for a range of between 3.8 and 7.3% by weight. (2014) on the catalytic decomposition of rigid polyurethane foam waste showed that ammonia, hydrogen cyanide and both nitrogen oxide and nitrogen dioxide were produced at temperatures up to 1100C. This can result from exposure to radiant and convected heat; visual obscuration due to smoke; inhalation of asphyxiant gases; and exposure to sensory/upper-respiratory irritants. The authors noted that the polyester polyols were more stable than the polyether polyols, with the latter fragmenting at a lower temperature (300400C).
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